1. Field of the Invention
The present invention relates to an electronic device and a radio timepiece each including an antenna.
2. Description of the Related Art
Conventionally, there is known an electronic device, such as a radio timepiece, including an antenna which receives a standard radio wave including time information, so as to automatically correct current time.
As the antenna which receives a standard radio wave including time information, for example, a bar antenna is often used, the bar antenna having a coil part formed by winding a conducting wire around a core made of a high-permeability magnetic material, such as an amorphous metal or ferrite.
However, when a component made of a metallic material, such as an electronic component or a ground pattern constituted of a copper foil, is disposed near the antenna, loss (eddy current loss) is caused thereby, and sensitivity (reception) of the antenna degrades.
Furthermore, when a terminal (for example, a terminal for checking, a check terminal hereinbelow) or an electronic component handling signals, the HIGH and LOW of which are switched at high speed, is disposed near the antenna, the sensitivity of the antenna degrades by being influenced by noise generated from the terminal or the electronic component.
Japanese Patent Application Laid-Open Publication No. 2010-273231 proposes cutting apart of a circuit substrate, the part including the circumference of the circuit substrate, so as to make a side part, and disposing an antenna on the side part of the circuit substrate.
With this configuration, an antenna can be some distance away from a component made of a metallic material, a terminal generating noise, or an electronic component, so that the sensitivity of the antenna can be prevented from degrading.
However, recently, an electronic device such as a radio watch has been having more functions. In order to realize various functions, it has been necessary to place many electronic components and/or terminals, such as a detection IC, a time microcomputer and various mechanical components, on a circuit substrate. In this point, the technology disclosed by Japanese Patent Application Laid-Open Publication No. 2010-273231 has a problem that because a space to dispose an antenna is secured by cutting a part of a circuit substrate, the area of the circuit substrate for placing electronic components and the like (packaging area) becomes small.
On the other hand, if an attempt is made to secure a large packaging area of a circuit substrate, the packaging area being for placing electronic components and the like, while bad influence from the electronic components or terminals on an antenna is avoided, it is necessary to dispose the antenna outside the circuit substrate. As a result, the size of an electronic device as a whole is increased.
Furthermore, Japanese Patent Application Laid-Open Publication No. hei 10-197662 (corresponding to U.S. patent application Ser. No. 08/997,405, abandoned) discloses a technology to dispose an electromagnetic shielding layer in the middle of a circuit wiring substrate on which an antenna is disposed.
However, when an electromagnetic shielding layer is disposed in the middle of a circuit wiring substrate on which an antenna is disposed, the sensitivity of the antenna becomes bad depending on a positional relationship between the antenna and the electromagnetic shielding layer.